1. Field of the Invention
The present invention relates to an image reading apparatus having a sheet guide path and an image processing system using the same. More particularly, the present invention relates to an image reading apparatus having a sheet guide path used as an image input device for a computer system for example. Further, the present invention relates to an image processing system using a sheet guide path, such as a photocopier, a facsimile machine, an image filing system, or a multifunctional image processing apparatus having functions such as a photocopier function, a facsimile function, etc.
2. Discussion of the Background
FIG. 1 is a schematic sectional view illustrating a conventional image reading apparatus 100. Referring to FIG. 1, de image reading apparatus 100 includes an optical image reading deuce 101, a sheet transport roller 102, a sheet discharge roller 103, a first pinch roller 104 opposing the sheet transport roller 102, a second pinch roller 105 opposing the sheet discharge roller 103, an upper sheet guide 106, and a lower sheet guide 107. Together with the upper sheet guide 106, the lower sheet guide 107 forms a sheet guide path denoted as “SGP,” which is a space between the sheet guides 106 and 107.
The sheet transport roller 102 and the sheet discharge roller 103 rotate in a clockwise direction. The first pinch roller 104 is pressed toward the sheet transport roller 102 with an appropriate pressure, and the second pinch roller 105 is pressed toward the sheet discharge roller 103 with an appropriate pressure. When no sheet is being fed, the first pinch roller 104 contacts the sheet transport roller 102, and the second pinch roller 105 contacts the sheet discharge roller 103. The first and second pinch rollers 104 and 105 rotate in a counter clockwise direction. When a sheet, S, is fed into the left side of the sheet guide path SGP in FIG. 1, the first pinch roller 104 presses the sheet S against the sheet transport roller 102, and the second pinch roller 105 presses the sheet S against the sheet discharge roller 103. Thus, the sheet of document S is transported along the sheet guide path SGP from the left side toward the right side of e sheet guide path SGP by the sheet transport roller 102 and the sheet discharge roller 103.
When the sheet S is transported over the optical image reading device 101, image information carried on a surface of the sheet, which is facing the optical image reading device 101, is read by the optical image reading device 101. Then, the sheet S is discharged from the image reading apparatus 100 by the sheet discharge roller 103.
Sometimes sheets carry dirt, dust or other particles or detritus such as fibers of paper, which have been rubbed off the surface of the sheet due to a rubbing motion between two sheets of a document Fibers of paper are also generated by a rubbing motion between a sheet of a document and a separating roller of a separating mechanism when the sheet is separated from the other sheets of the document. Sheets also carry other types of dirt or particles, such as particles of pencil lead, particles of an eraser, particles of ink, particles of photocopier toner, lint, etc. Referring back to FIG. 1, particles of dirt D3, D4, and D5 are adhered to the sheet S, and particles of dirt D1 and D2 are particles that have dropped off front sheets of a document and have piled up on the optical image reading device 101. As used herein, the term “dirt” includes any dust detritus, or other particles carried on sheets of paper that pass through the sheet guide path. When the optical image reading device 101 becomes soiled by dirt, the optical image reading device 101 may erroneously read information on the sheet S.
Japanese Laid-Open Patent Publication No. 09027889 describes a document reader that has two pairs of sheet carrying rollers, a backup roller, and a platen glass. The platen glass is further downwardly placed opposing the backup roller kept with a gap of 1 mm or over to avoid adhesion of dust on the platen glass. However, Japanese Laid-Open Patent Publication No. 09027889 does not disclose a device that prevents dirt on a sheet from reaching a reading portion, including the platen glass.
Japanese Laid-Open Patent Publication No. 09055828 describes an image reader mechanism that has a contact image sensor (CIS), a CIS roller, a cam, a spring presser, a motor, and a control unit. The control unit monitors an output signal waveform of the CIS. When the output signal waveform of the CIS is lowered, the control unit determines that a glass surface of the CIS is stained. Then, the control unit activates the motor and the cam such that the spring presser presses the CIS against the CIS roller to clean the glass surface of the CLS. However, Japanese Laid-Open Patent Publication No. 09055828 does not describe a device that prevents dirt on a sheet from reaching the glass surface of the CIS.
Japanese Laid-Open Patent Publication No. 09065050 describes an original document reader that has a contact type image sensor, a roller shaped white elastic fiction body, and washing pads. When the contact type image sensor senses whether the roller sped white elastic friction body or the contact type image sensor is blackened, the washing pads are applied with detergent and then put into contact with the roller shed white elastic friction body to remove dirt on the surfaces of the roller shaped white elastic friction body and the contact type image sensor. However, Japanese Laid-Open Patent Publication No. 09065050 does not describe a device to prevent dirt on a sheet of document reaches at the roller shaped white elastic friction body and the contact type image sensor.
In the above described apparatuses, sheets can still carry dirt to image reading portions of the apparatuses. Therefore, it is likely that the image reading portions of those apparatuses will be soiled during normal operation.